Principal Risks [Member] Not A Complete Investment Program [Member] Investment And Market Risk [Member] Management Risk [Member] Distribution Risk [Member] Municipal Securities Risk [Member] When Issued And Delayed Delivery Transactions Risk [Member] Debt Instruments Risk [Member] Municipal Conduit Bond Risk [Member] Corporate Bond Risk [Member] Project Finance Risk [Member] Risks Of Investing In Debt Issued By Non Profit Institutions [Member] Taxable Municipal Securities Risk [Member] Build America Bonds Risk [Member] Income and Distribution Rate Risk [Member] Income Securities Risk [Member] Issuer Risk [Member] Spread Risk [Member] Credit Risk [Member] Current Fixed-Income and Debt Market Conditions [Member] Reinvestment Risk [Member] Extension Risk [Member] Prepayment Risk [Member] Valuation of Certain Income Securities Risk [Member] Duration Management Risk [Member] Financial Leverage And Leveraged Transactions Risk [Member] Inflation Or Deflation Risk [Member] Insurance Risk [Member] Below Investment Grade Securities Risk [Member] Repurchase Agreement Risk [Member] Sector Risk [Member] Short Sales Risk [Member] Special Risks Related To Municipal Securities [Member] Structured Finance Investments Risk [Member] Asset Backed Securities Risk [Member] Mortgage Backed Securities Risk [Member] Commercial Mortgage Backed Securities Risk [Member] Residential Mortgage Backed Securities Risk [Member] Sub Prime Mortgage Market Risk [Member] C L O C D O And C B O Risk [Member] C L O Subordinated Notes Risk [Member] Risks Associated With Risk Linked Securities [Member] Risks Associated With Structured Notes [Member] Senior Loans Risk [Member] Second Lien Loans Risk [Member] Subordinated Secured Loans Risk [Member] Unsecured Loans Risk [Member] Loans And Loan Participation And Assignments Risk [Member] Mezzanine Investments Risk [Member] Unfunded Commitments Risk [Member] Distressed And Defaulted Securities Risk [Member] Preferred Securities Risk [Member] Convertible Securities Risk [Member] Private Credit Assets Risk [Member] Liquidity Risk [Member] Volatility Risk [Member] Inverse Floating Rate Securities Risk [Member] Sovereign Debt Risk [Member] Strategic Transactions Risk [Member] Synthetic Investments Risk [Member] Counterparty Risk [Member] Securities Lending Risk [Member] Private Securities Risk [Member] Risks Associated with Private Company Investments [Member] Investment Funds Risk [Member] Market Discount and Price Volatility Risk [Member] Dilution Risk [Member] Availability And Quality Of Data Risk [Member] Portfolio Turnover Risk [Member] Recent Market Developments Risk [Member] Increasing Government And Other Public Debt Risk [Member] Legislation And Regulation Risk [Member] Risk Of Failure To Quality As A R I C [Member] Conflict Of Interest Risk [Member] Market Disruption And Geopolitcal Risk [Member] Cyber Security Market Disruption And Operational Risk [Member] Anti Takeover Provisions Risk [Member]